Retinoscopy Flashcards
what is an objective measurement?
a measurement and evaluation you make as a doctor with limited patient involvement
examples of objective measurements in assessment of refractive error
- keratometry
- retinoscopy
- autorefraction
examples of subjective measurements in assessment of refractive error
manifest (subjective) refraction
what is a subjective measurement?
when a subject participates in this data collection, doctor is in charge but patient guides evaluation
image point, when an object is at infinity, is where
light rays converge in the back of the eye
when light is coming IN to the system
another name for the far point is the:
anterior focal point
what is the far point?
the location of the farthest object on which the fully relaxed eye can focus
what type of rays from the retina are involved in far point?
diverging rays from the retina
when light is going OUT of the system
image point and far point for:
Emmetropia
image point: at the retina
far point: at infinity
image point and far point for:
Myopia
image point: in front of the retina
far point: closer than infinity
image point and far point for:
Hyperopia
image point: behind the retina
far point: “beyond” infinity
what are the two factors that contribute to Ametropia?
- power of the optical system (cornea + lens)
- axial length of the eye (distance to retina/ screen)
how does the “power of the optical system” influence ametropia in the case of myopia?
the more “plus” in a system, the more “powerful” the eye, and light rays converge sooner (in myopia)
how does “Axial length of the eye” influence ametropia in the case of hyperopia?
the shorter the distance from the front of the eye to the retina, the less distance rays have to converge, and so they may not be fully converged at the retina (in hyperopia)
what is astigmatism?
when there are two image “points” that are really image lines
importance of meridians in astigmatism
- two principle meridians that give rise to two image lines
- one meridian will focus in front of the other (Can be either horizontal or vertical line)
where can the line images in astigmatism be?
these line images can either be in front of the retina, behind the retina, or one of them on the retina
where are image “points” (lines) in:
simple myopic astigmatism
one at the retina
one in front of the retina
where are image “points” (lines) in:
simple hyperopic astigmatism
one at the retina
one behind retina
where are image “points” (lines) in:
compound hyperopic astigmatism
both behind the retina
where are image “points” (lines) in:
compound myopic astigmatism
both in front of the retina
where are image “points” (lines) in:
mixed astigmatism
one in front and one behind
goal of retinoscopy is to
objectively neutralize the patient’s refractive error
retinoscopy is done by placing the ___ point where?
far point of the patient’s principle meridian(s) coincident with the doctor’s retinoscope
moving the streak of the retinoscope across the patient’s eye produces a
a movement of the patient’s retinal reflex
when does this “neutralization” of the movement occur?
when the lenses used by the doctor place the patient’s far point at their retinoscope (working distance)
with-motion is observed when the far point of the eye is:
behind the viewing aperture
between the aperture and infinity
against-motion is observed when the far point of the eye is:
between the eye and the viewing aperture
neutral motion is observed when the:
retina and the aperture are in conjugate focus
the features of the retinoscopic reflex are affected by:
the location of the eye’s far point in relation to the viewing aperture of the retinoscope
as the far point moves closer/further from the aperture, what features may be affected?
width, brightness, and speed of the reflex
as the far point moves closer to the aperture, what occurs to the reflex features?
the width, brightness, and speed of the reflex increase
what meridian is being evaluated when the retinoscope is oriented vertically?
180 degree meridian is evaluated
what meridian is being evaluated when the retinoscope streak is oriented horizontally?
90 degree meridian is evaluated
what is it called when the reflex is misaligned with the stream beam?
break
what is it called when the movement of the reflex is misaligned with the stream beam?
skew
what occurs to the brightness when reflex is misaligned with the streak beam?
reflex is dimmer
what occurs to the width of the reflex when it is misaligned with the steak beam?
the reflex is wider with less defined margins
what is the working distance? how is it measured?
it is the distance from the eye that you hold your retinoscope, and it is based on the length of your arm
what are the 2 working distances?
- 5D for 67cm or
2. 0D for 50cm
if the far point of the patient’s eye is behind your scope, you will see ____ motion
with motion
see with motion -> add what power?
plus power
see against motion -> add what power?
minus power
if the far point of the patient’s eye is in front of your scope, you will see _____ motion
against
the gross findings for retinoscopy is when:
lenses are in place that allow “neutral” motion to be seen in all meridians
-far point(s) at plane of retinoscope
steps of retinoscopy:
- scan all meridians of the eye
- determine the most plus (least negative) meridian and neutralize that meridian first
- once all meridians ar neutralized (gross findings), remove your working distance lens to determine the patient’s refractive correction (net findings)
what kind of motion do you see in emmetropes and what does that mean?
see with motion, which means the far point is behind
